#define  _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
int main()
{
    char a = 0;
    scanf("%c", &a);
    if ((a >= 'a' && a <= 'z') || (a >= 'A' && a <= 'Z'))
    {
        printf("YES\n");

    }
    else
    {
        printf("NO\n");
    }
    return 0;
}